Voltage and current controllable electrical power supplies are known. Some of the most expensive and user controllable power supplies have sensitive precise scientific adjustment capabilities. Smaller power supplies are available for inexpensive personal electronics as a battery replacement. However these generic battery replacements have the ability to output discrete voltage based upon a selector switch. The selector switch typically has discrete voltage selection in multiples of battery cell values, such as 3 volts, 4.5 volts, 6 volts, 9 volts and 12 volts. Such user adjustable supplies can damage equipment if the selector switch is improperly set, either too high or too low. The one saving grace of small battery replacement supplies is the low current capability. An improper setting will cause damage typically limited by the low current capability of the device.
Personal computers, however, have a much higher current demand. Most personal computer and lap top power supplies are specialized with specific voltage and current requirements. It is especially because the power capability is higher, that the results of placing a choice of voltage and current capability in the user's hands can cause such significant damage. Further, the destruction and damage would be expensive as the destruction of components of personal computers and laptops are much more costly than the destruction of most personal electronic equipment.
An earlier power converter for personal electronics equipment was seen in U.S. Pat. No. 5,347,211, incorporated by reference herein. In the scheme set forth in this reference, users were provided with a key which had an electrical component which was sensed by the main control circuitry. The voltage output was proportional to the value of a resistor in an insertable structure. Since the output of the power supply was proportional to the value of resistance, the isolation of control could be circumvented by providing an insertion structure with a variable resistance, isolation could easily be circumvented.
Given the value and importance of personal computers and lap tops, what is needed is a system by which control of the voltage and current output of a power supply may be effectively isolated. The mechanism of isolation should not be amenable to easy circumvention.